A conventional hearing aid comprised a main body case, a battery case that is provided so that it can be pulled from inside the main body case to the outside of the main body case, a control device that is actuated by the electromotive force of the air battery held in the battery case, a microphone and a speaker that are electrically connected to the control device, and switching part for cutting off the supply of power from the air battery to the control device when the battery case is pulled out of the main body case. For example, in a so-called storage state, in which the hearing aid is removed from the ear, such as when the user is sleeping, the battery case is pulled out of the main body case when the hearing aid is removed from the ear, whereupon a switching part cuts off the supply of power from the air battery to the control device. Consequently, a conventional constitution suppressed a decrease in the capacity of the air battery.
However, even when the supply of power from the air battery to the control device has been cut off by the switching part, the air battery is still open at its air holes, so the chemical reaction with oxygen continues, and the battery capacity gradually decreases.
For example, Patent Literature 1 discloses a technique in which a switching part is opened and closed by a manipulation member provided to the outer face of the main body case, and the air holes in the air battery are opened and closed with a lid portion.